Laboratory diagnosis of influenza and the impact of the pandemic (H1N1) 2009 virus

Aetiological confirmation of respiratory tract infections in patients facilitates appropriate antimicrobial use and infection control procedures. From a public health perspective, the laboratory confirmation of influenza allows assessment of circulating viruses, community attack rates and the efficacy of vaccination programs, while assisting modelling as part of pandemic preparedness planning. Rapid antigen and immunofluorescent antigen tests are relatively insensitive in detecting pandemic (H1N1) 2009 influenza compared to seasonal subtypes, and influenza subtype-specific nucleic acid amplification tests should be used as the 'gold-standard' for diagnosis. Pathogen-specific serological testing aids the retrospective diagnosis of infection, and is used in seroprevalence studies. Influenza virus isolation is needed for vaccine assessment and formulation. Although some challenges surrounding diagnostic testing during pandemic (H1N1) 2009 have been resolved, others remain; this may test laboratories again in future pandemics.